It is not clear to me, if the messages reported after closure are the only ones, or there are more.

In case there are only such messages, there is an high chance that the layout updated events are caused by the fact that binings are 'released'. Once the binding is no more in place, every databound control will revert to the default value and, in case of
a TextBlock, it would trigger a layout pass (it seems), which invalidates the parent layout (this is confirmed by the fact that the first LayoutUpdated comes from the TextBlock).

I haven't checked if such layout pass after closing happens just in SL or in WPF too, but I would try to implement the finalizer on the view, call a couple of GC.Collect() and verify if the object is properly reclaimed by the GC.

I implemented the finalizer in the view and the memory is properly reclaimed by the GC. However, I still don't understand why the LayoutUpdated event is still being raised for Views that were previously closed. From the debug output above the views with
hash codes ﻿﻿64479624 and 27440617 somehow are still active even though they do not show up. Only the newly created DialogAView shows up on the screen. What I mean is that these two instances of DialogAView will continue to call layout updated every time I
click on ShowWindow. Any ideas?

As far as I understand, you use a toolbar item to display a new dialog, and you keep on creating and closing new dialogs; moreover, in your repro-project layout updated events are raised for dialogs that are previously closed, until next garbage collection.
Am I correct? I'm trying to figure how CM could be related to such behaviour, but honestly, I doubt that this is caused by the framework... LayoutUpdated events are raised as a consequence of calling InvalidateArrange, and such action is tipically handled
by the WPF/SL engine (this could be a typical effect of using WeakEvents, that are kept alive until the control is garbage collected). Is it possible that this behaviour is related to the ChildWindow itself? You could try to reproduce the same scenario without
CM and see what happens.